1. Field of the Invention
The present invention relates to a semiconductor device and a method for packaging a semiconductor chip, and more specifically to a method of packaging a semiconductor chip including high frequency transistors or others, for instance.
2. Description of the Background Art
Conventionally, a wire bonding method is so far well known as the method of packaging a semiconductor chip (e.g., IC chip) as a package, as shown in FIGS. 1 and 2, in which FIG. 1 is an internal plan view showing a packaged IC chip, and FIG. 2 is an internal side view thereof.
In more detail, when an IC chip is packaged, first the IC chip 103 is secured with its face up on a ground pattern 102 formed on a surface of a ceramic substrate 101 as shown in FIG. 1. Then, pad portions (aluminum electrodes) 104 of the IC chip 103 are connected to package terminals 105 by bonding, e.g. thermo-compression bonding or ultrasonic bonding, wires 106 such as Au or A1 therebetween. After that, the IC chip 103 is sealed with a cap 107 made of ceramic or metal, as shown in FIG. 2. Further, external leads (not shown) are taken out of the package terminals 105 to complete a packaged semiconductor device.
In the above-mentioned conventional packaging method, however, since the IC chip is connected by bonding wires and in addition sealed by the cap, there exists such a problem in that it is difficult to reduce the thickness of the packaged semiconductor device, though the reduction is strongly desired for packaging of chips.
To overcome this problem; that is, to reduce the thickness of the packaged semiconductor device, there has been so far known such a method that an IC chip 112 is mounted on the surface of a substrate 111; electrodes of the IC chip 112 are connected to external leads 113 by wires 114; and all the elements are molded by a resin 115 as a package, as shown in FIG. 3.
In this chip packaging method, however, since the IC chip is molded only by the resin 115 having no shield effect which the ceramic cap or other has, there arises another method in that the IC chip emits radio waves to the outside or is subjected to the influence of radio waves coming from the outside.
As described above, in the prior art semiconductor chip packaging method, it has been impossible to reduce the thickness of the package, without deteriorating the shielding effect.